Structure of chromatin and the linking number of DNA.

作者：Abraham Worcel, Steven H. Strogatz, D Riley · 发表于：Proceedings of the National Academy of Sciences · 年份：1981 · DOI：10.1073/pnas.78.3.1461 · 被引用次数：222 · 研究领域：DNA and Nucleic Acid Chemistry、Genomics and Chromatin Dynamics、RNA and protein synthesis mechanisms

Recent observations suggest that the basic supranucleosomal structure of chromatin is a zigzag helical ribbon with a repeat unit made of two nucleosomes connected by a relaxed spacer DNA. A remarkable feature of one particular ribbon is that it solves the apparent paradox between the number of DNA turns per nucleosome and the total linking number of a nucleosome-containing closed circular DNA molecule. We show here that the repeat unit of the proposed structure, which contains two nucleosomes with -1 3/4 DNA turns per nucleosome and one spacer crossover per repeat, contributes -2 to the linking number of closed circular DNA. Space-filling models show that the cylindrical 250-A chromatin fiber can be generated by twisting the ribbon.